Loss of colour, loss of lip and red gills!

Okay so i noticed one of my mickeymouse platys was sat on the bottom, up until this morning everything was fine seemed normal but all of a sudden ive noticed its changed in colour, water testing shows up fine, no other fish affected in tank, the mickey mouse has now been taken out and put into a 12 litre quarantine tank and being treated for finrot and bacterial infection (as its the only medicine i had readily to hand) okay so stats and pics below